Incubating Eggs: 35 days
As soon as the first egg is laid, the female and the male take turns incubating. Both male and female eagles form a brood patch--a bare spot on their tummy where they can press their hot skin directly against the eggs or chicks to keep them warm. The female's brood patch is a little bigger and more feather-free than the male's. And the female incubates the eggs more often than the male does.
One study showed that the female was responsible for 72% of the incubation.
Incubating lasts about 35 days.
Once incubation begins, the male and female take turns sitting on the eggs, but the female does the bulk of the work. The incubation period lasts for over a month (34-36 days).
Eagles typically lay 2 eggs, sometimes 3. The first egg is laid a day or two before the 2nd, and sometimes the third is a full week behind the first. Because incubation begins as soon as the first egg is laid, this means the young hatch at different times. This may ensure that at least one young will survive and fledge, as it will get the first food and be the strongest. If food is not a limiting factor in a particular year, more of the eaglets will likely survive. In some species of eagles, only one young typically survives, but in bald eagles it is very common for 2 or even 3 to survive and fledge.
Females lay one to three eggs, which hatch at approximately 35 days. Both parents share in the incubation and feeding of the young. In July, somewhere between 10 and 14 weeks after the babies hatch, they’re ready leave the nest, but the parents will continue to feed and care for them until September or even October.
Caption Page: Sitting on Eggs
Eagles sit on their eggs most of the time--one study showed that the eggs were incubated 98% of the time! But when the temperature is warm and there is little wind, the parents incubate less often. Sometimes when the parents leave the eggs, they cover them with feathers and nesting materials. Scientists don't know for sure whether they do this to keep the eggs warm or to hide the eggs so predators don't steal them.
Eagles have VERY sharp claws on their powerful talons. When the incubating parent is moving about the nest, it often clenches its talons so the sharp claws can't hurt the eggs or babies by accident. The parents are also very careful to step around the eggs to avoid crushing them. Parents probably turn the eggs at least once a day, but scientists aren't sure how often this happens or which parent does it.
Facts and Photos